As title suggests, When you save and quit the world and see world list again, the world you just quit is no longer there ( early gave me a heart attack to see it missing). This happens with any world, so not world specific. The played worlds just don't appear until i restart the whole game. When i closely monitored it, i noticed that minecraft doesn't delete session.lock file even after world is saved and quited. So game just doesn't show it. Temporary solution is to go to the "yourworld" folder and delete session.lock file manually, then world just appears without restarts and works normally.

Conclusion:

Problem is caused as game doesn't delete session.lock and "save and quit to title". When its deleted manually everything is normal then.

Fix: game should delete that file after save amd quit automatically so world appears in list normally

Pls look into this